Light emitting device

ABSTRACT

A light emitting device includes: a plurality of laser elements including a first laser element and a second laser element; a case enclosing the laser elements and including a light-transmissive region; and a plurality of main lenses including a first main lens configured to collimate or converge light emitted from the first laser element and a second main lens configured to collimate or converge light emitted from the second laser element. At least a first portion of the light-transmissive region is disposed on a first imaginary line passing through a light emitting end surface of the first laser element and the first main lens, and at least a second portion of the light-transmissive region is disposed on a second imaginary line passing through a light emitting end surface of the second laser element and the second main lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/069,299, filed Oct. 13, 2020, which claims priority under 35U. S. C. § 119 to Japanese Patent Application No. 2019-198334, filedOct. 31, 2019. The contents of these applications are herebyincorporated by reference in their entireties.

BACKGROUND

The present disclosure relates to a light emitting device that includesa plurality of light emitting elements and a plurality of lenses.

A light emitting device having a plurality of semiconductor laserelements and a lens array is, for example, described in JP 2007-019301A.

SUMMARY

JP 2007-019301A describes that, when the position of each light emittingregion of two semiconductor laser elements has a mounting error, theangle of tilt of the lens array is adjusted to increase the parallelismof the collimated light. However, merely adjusting the tilt angle of thelens array may not enough to sufficiently improve the adjustmentaccuracy. Accordingly, a light emitting device allowing furtherimprovement of adjustment accuracy has been needed.

A light emitting device according to one embodiment of the presentdisclosure includes a plurality of light emitting elements including afirst light emitting element and a second light emitting element, a caseenclosing the plurality of light emitting elements, the case having alight-transmissive region allowing light emitted from the plurality oflight emitting elements to pass through, a plurality of main lensescovering at least a portion of the light-transmissive region, theplurality of main lenses including a first main lens to collimate orconverge light emitted from the first light emitting element and asecond main lens to collimate or converge light emitted from the secondlight emitting element, and a plurality of sub-lenses disposed in thecase, the plurality of sub-lenses including a first sub-lens located inan optical path between the first light emitting element and the firstmain lens and a second sub-lens located in an optical path between thesecond light emitting element and the second lens.

With the light emitting device described above, the light emittedthrough the main lenses can be within a target quality range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a light emitting device havinga plurality of light emitting elements and a plurality of collimatinglenses, but not having a sub-lens.

FIG. 2 is a diagram schematically illustrating a plurality of lightemitting elements emitting light with different diverging angles in alight emitting device that does not have a sub-lens.

FIG. 3 is a diagram schematically showing a basic configuration of alight emitting device according to one embodiment of the presentdisclosure.

FIG. 4A is a schematic perspective view of a light emitting deviceaccording to a first embodiment of the present disclosure.

FIG. 4B is a schematic perspective view showing an interior of a lightemitting device according to the first embodiment.

FIG. 5A is a schematic top view of a light emitting device according tothe first embodiment, viewed from the positive side of the Z-axis.

FIG. 5B is a schematic side view of the light emitting device accordingto the first embodiment, viewed from the positive side of the X-axis.

FIG. 5C is a schematic side view of the light emitting device accordingto the first embodiment, viewed from the positive side of the Y-axis.

FIG. 6 is a schematic cross-sectional view of a light emitting deviceaccording to the first embodiment.

FIG. 7 is a schematic plan view showing an internal configuration of alight emitting device according to the first embodiment.

FIG. 8 is a schematic perspective view showing an example of a lensarray that can be used in the light emitting device according to thefirst embodiment.

FIG. 9A is a schematic perspective view of a light emitting deviceaccording to a second embodiment of the present disclosure.

FIG. 9B is a schematic perspective view showing an interior of a lightemitting device according to the second embodiment.

FIG. 10A is a schematic top view of a light emitting device according tothe second embodiment, viewed from the positive side of the Z-axis.

FIG. 10B is a schematic side view of the light emitting device accordingto the second embodiment, viewed from the positive side of the X-axis.

FIG. 10C is a schematic side view of the light emitting device accordingto the second embodiment, viewed from the positive side of the Y-axis.

FIG. 11 is a schematic cross-sectional view of the light emitting deviceshown in FIG. 9A.

FIG. 12 is a schematic plan view showing an internal configuration of alight emitting device shown in FIG. 9A.

FIG. 13A is a schematic perspective view showing a light emitting deviceaccording to a third embodiment of the present disclosure.

FIG. 13B is a schematic perspective view showing an interior of thelight emitting device shown in FIG. 13A.

FIG. 14A is a schematic top view of a light emitting device according tothe third embodiment, viewed from the positive side of the Z-axis.

FIG. 14B is a schematic side view of the light emitting device accordingto the third embodiment, viewed from the positive side of the X-axis.

FIG. 14C is a schematic side view of the light emitting device accordingto the third embodiment, viewed from the positive side of the Y-axis.

FIG. 15 is a schematic cross-sectional view of a light emitting deviceaccording to the third embodiment.

FIG. 16 is a schematic plan view showing an internal configuration of alight emitting device according to the third embodiment.

DETAILED DESCRIPTION

Before describing embodiments of the present disclosure, related art andfindings obtained by the present inventors will be described.

With reference to FIG. 1 and FIG. 2 , difficulties that may occur in alight emitting device configured to collimate or diverge light emittedfrom a plurality of light emitting elements by using a plurality oflenses will be described.

FIG. 1 is a diagram schematically showing a configuration of a lightemitting device 100P having a plurality of laser diodes 110 and aplurality of lenses 140. The light emitting device 100P does not havesub-lenses, such that light L emitted from each of the laser diodes 110reaches a corresponding one of the lenses 140. The lenses 140 employedin this example are optical elements configured to collimate light Lemitted from a corresponding one of the laser diodes 110. In this case,the light emitting device 100P is designed to collimate the light fromeach lens 140 into a substantially parallel beam shape. Therefore, thedesign position and orientation of each laser diode 110 is determinedsuch that the “light emitting region” at the emission edge of each oflaser diode 110 is aligned with or near the focal point of the lens 140and the center portion of the light L perpendicular to the lightincidence surface of lens 140. The light-emitting region of a laserdiode is also referred to as the emitter region. In the descriptionbelow, the design position of the light emitting region may be referredto as the target position. The target position of the light-emittingregion of each laser diode 110 does not necessarily have to be exactlythe same as the focal point of lens 140, and can be determined to form adesired light beam. For example, to control the beam shape of collimatedlight L, a target position may be intentionally set to slightly awayfrom the focal point and place the light emitting region at that targetposition. In such a case, it is necessary to accurately position thelight emitting region of the laser diode 110 at the design position,that is, the target position determined based on the optical design.

When mounting the laser diode 110, the position of laser diode 110 maydeviate from the target position. Such a positional deviation can becaused by variations in the mounting of the laser diode 110. If thelaser diode 110 deviates from its design position, such as the lightemitting region offset from the target position, the direction and/ordiverging angle of light passing through the lens 140 may deviate fromthe designed range. In the example shown in FIG. 1 , the light-emittingregion of each laser diode 110 is out of the target position, by whichthe light beam passing through the lens 140 is not collimated asdesigned, and the direction and diverging angle of the light beam areout of the target.

The positional deviation of the laser diodes 110 can occur separately ateach laser diode 110. After mounting the laser diodes 110, if theposition or orientation of individual lenses 140 can be adjusted tomatch the position of the light emitting region, desired collimationlight can be obtained. However, if each lens 140 is secured to a commonmember or formed from the same material monolithically, such individualadjustments cannot be performed. Also, if the lenses 140 are secured onthe light-transmissive member of the package, a smaller range is allowedfor adjusting each lens 140, so the alignment of individual lens 140 maynot be able to compensate for the positional deviation of the lightemission area.

FIG. 2 is a diagram schematically illustrating a plurality of laserdiodes 110 in the light emitting device 100P emitting light L withdifferent diverging angles. As in the example illustrated in FIG. 1 ,the light emitting device 100P illustrated in FIG. 2 does not have asub-lens. The laser diodes 110 emit light L with uneven divergingangles, for example, when the laser diodes 110 emit light of differentcolors. In such a case, the structures and sizes of the laser diodes 110may differ from one another, and accordingly, the diverging angles ofthe emitted light may from one another. In such a case, the beamdiameters of the light beam passing through the lenses 140 may differfrom one another. In order to obtain collimated lights of closelyuniform beam diameters by changing the focal distances of the lens 140according to the types of laser diodes 110, the size of the lightemitting device 100P along the optical axis must be increased.

Such concerns may occur not only when various types of laser diodes 110are combined with lenses, but also when various types of light emittingelements are combined with lenses.

Basic Configuration

Certain embodiments of the present disclosure will be described belowwith reference to the drawings. An example of a basic configuration of alight emitting device common to certain embodiments will be describedwith reference to FIG. 3 . FIG. 3 is a diagram schematically showing anexample of a configuration of a light emitting device. In certaindrawings, an X-axis, a Y-axis, and a Z-axis that are orthogonal to oneanother are schematically shown for reference. The orientation of thelight emitting device during use is arbitrary and is not limited by theorientation of the light emitting device shown in the drawings.

The light emitting device 100 includes a plurality of light emittingelements 10, including a first light emitting element 10A and a secondlight emitting element 10B, and a case 20, which encloses the pluralityof light emitting elements 10. The plurality of light emitting elements10 may be hermetically sealed by the case 20. Although two lightemitting elements 10 are illustrated in FIG. 3 , the number of the lightemitting elements 10 may be three or more, as shown in other examplesillustrated below. The light emitting elements 10 may be laser elements,such as edge-emitting semiconductor laser elements or vertical cavitysurface emitting laser (VCSEL) elements. For such laser elements, laserdiodes (LDs) having semiconductor layers can be used. Light emittingelements 10 may be light emitting light emitting diodes (LEDs)configured to emit incoherent light. The light emitting elements 10 arepreferably laser elements, because a laser light emitted from a laserelement has higher rectilinear propagation than light emitted from anLED, allowing more light to be irradiated into the lens. The term“light-emitting region” of each of the light emitting element 10 refersto a region in a surface of each of the light emitting elements 10 fromwhere light L is emitted. When the light emitting elements 10 are laserelements, the term “light-emitting region” of each of the light emittingelements 10 refers to a region in a surface of each of the lightemitting elements 10 from where a laser beam is emitted. The lightemitted from each of the light emitting elements 10 is visible light,for example. The wavelength of the light is not limited to the visiblelight range, but can be in the infrared or ultraviolet range. Inaddition, the plurality of light emitting elements 10 may respectivelyemit light in different wavelength ranges or may respectively emit lightof different colors. In the example shown in FIG. 3 , the peakwavelength of the light emitted from the first light emitting element10A is different from the peak wavelength of the light emitted from thesecond light emitting element 10B.

The case 20 has a light-transmissive region 30 to allow the light Lemitted from the plurality of light emitting elements 10 to passtherethrough. The light-transmissive region 30 is, for example, formedwith glass. The case 20 may be referred to as a package. A specificexample of the configuration of the case 20 will be described below.

The light emitting device 100 has a plurality of main lenses 40respectively covering at least portions of the light-transmissive region30. The plurality of main lenses 40 include a first main lens 40Aconfigured to collimate or converge the light L emitted from the firstlight emitting element 10A, and a second main lens 40B configured tocollimate or converge the light L emitted from the second light emittingelement 10B. In the example shown in FIG. 3 , the main lenses 40 arecollimating lenses.

Further, the light emitting device 100 has a plurality of sub-lenses 50disposed in the interior of the case 20. The plurality of sub-lenses 50include a first sub-lens 50A disposed in an optical path between thefirst light emitting element 10A and the first main lens 40A, and asecond sub-lens 50B disposed in an optical path between the second lightemitting element 10B and the second main lens 40B. Accordingly, thelight emitted from the first light emitting element 10A passes throughthe first sub-lens 50A and enters the first main lens 40A. The firstsub-lens 50A provides an auxiliary function of the first main lens 40A.The first main lens 40A in combination with the first sub-lens 50A canachieve a desired collimation or conversion. Similarly, the lightemitted from the second light emitting element 10B passes through thesecond sub-lens 50B and enters the second main lens 40B. The secondsub-lens 50B provides an auxiliary function of the second main lens 40B.The second main lens 40B in combination with the second sub-lens 50B canachieve a desired collimation or conversion. Accordingly, the mainlenses 40 used in combination with the sub-lenses 50 may have a shapedifferent from that of the main lenses used without the sub-lenses 50.

In FIG. 3 , light L emitted from each of the light emitting element isrepresented graphically by the area enclosed by two dashed lines. Theintensity of light L, such as a laser beam, can be approximatelyrepresented as, for example, a Gaussian distribution at a planeperpendicular to the direction of propagation of the center of the lightL. The diameter of the beam of such light L can be determined by thesize of the region with the light intensity, for example, equal orgreater than 1/e², relative to the light intensity of the center of thebeam, where “e” is Napier's constant (about 2.71). The diameter of thebeam may be defined by other criteria.

The plurality of sub-lenses 50 can be disposed independently of eachother in the case 20. Therefore, the position and orientation of theindividual sub-lenses 50 can be adjusted without being constrained toeach other. In FIG. 3 , components supporting the sub-lenses 50 are notshown for simplicity. The individual sub-lenses 50 can be secureddirectly or indirectly to the case 20.

The position and orientation of the first sub-lens 50A are determinedaccording to the position and orientation of the first light-emittingelement 10A after the first light emitting element 10A is disposed inthe case 20. Similarly, the position and orientation of the secondsub-lens 50B are determined according to the position and orientation ofthe second light-emitting element 10B after the second light emittingelement 10B is disposed in the case 20. The plurality of sub-lenses 50can each compensate positional deviation and/or orientation deviation ofthe plurality of light emitting elements 10. Also, even when theplurality of light emitting elements 10 are disposed without positionaldeviation, differences in the beam diameters or in the conversion pointof the light may occur due to differences in the properties such aswavelengths and diverging angles of light emitted from the plurality oflight emitting element 10. Such differences in the beam diameter or inthe conversion point of light emitted from each of the plurality oflight emitting elements 10 can be adjusted by a respective correspondingone of the plurality of sub-lenses 50. From these features, thesub-lenses 50 may be referred to as correcting lenses or adjustinglenses.

Adjustment of the position and orientation of each of the sub-lenses 50can be performed by measuring light L passing through the sub-lens 50 byusing a device such as a beam profiler, while maintaining emission oflight L from the light emitting element 10. For example, when anultraviolet curable resin is used to secure the sub-lenses 50 to thecase 20, the adjustment described above is carried out with the uncuredultraviolet curable resin between the sub-lenses 50 and the case 20.After determining the position and orientation of the sub-lenses 50, theresin can be cured by irradiating ultraviolet light to the resin whilemaintaining the positions and orientations of the sub-lenses 50 by usinga jig or a holding device. Instead of using the resin, a bondingmaterial containing a metal that is softened or melted by heating may beused. Adjusting the direction and/or diverging angle of light L emittedfrom the light emitting device 100 by disposing the sub-lenses 50 whilemaintaining emission of light L from the light emitting elements 10 canbe referred to as “active alignment.” After such active alignment iscompleted, the main lenses 40 are disposed.

Lights L that have been corrected through the sub-lenses 50 enter themain lenses 40 respectively. This allows the lights passed through themain lenses 40 to be within the target quality range. The quality oflight includes propagating direction of light, diverging angle of light,and intensity of light. The expression “within the target quality” meansone or more of these are within the target range, and it is preferablethat all of them are within the target range.

In addition, even if the main lenses 40 are provided as a lens array inwhich the main lenses 40 are connected to one other, it is possible toobtain a plurality of light beams each satisfying the desired quality,by adjusting the position of the lens array within a range that isallowed for the lens array.

In FIG. 3 , the main lenses 40 are secured directly or indirectly to anoutside of the case 20. If the main lenses 40 are disposed to theinterior of the case 20, the light collimated or converged by the mainlenses 40 are extracted to the outside of the case 20 through thelight-transmissive region 30. In such a case, the possibility ofdegradation in the quality of the light beam caused by thelight-transmissive region 30 cannot be ruled out. Therefore, it ispreferable to dispose the main lenses 40 outside of the case 20 as shownin FIG. 3 . With this arrangement, degradation in the quality of thelight beams can be reduced or avoided. Meanwhile, the sub-lenses 50 aredisposed to the interior of the case 20, not to the outside. The light Lemitted from each of the light emitting elements 10 spreads in a widerrange as the distance from the light emitting region increases. Bydisposing the sub-lenses 50 inside the case 20, the sub-lenses 50 can beplaced closer to the light-emitting regions of the light emittingelements 10, which allows the correction by the sub-lenses 50 havingdimensions smaller than that required for the sub-lenses 50 placedoutside of the case 20. This can be advantageous for miniaturizing thelight emitting device 100.

First Embodiment

A first embodiment will be described below with reference to FIG. 4Athrough FIG. 8 .

A general structure of a light emitting device 100 according to thefirst embodiment will be described below with reference to FIG. 4A, FIG.4B, FIG. 5A, FIG. 5B, and FIG. 5C. FIG. 4A is a schematic perspectiveview of a light emitting device according to the first embodiment. FIG.4B is a schematic perspective view showing an interior of the lightemitting device 100 according to the first embodiment. FIG. 5A is aschematic top view of a light emitting device 100 according to the firstembodiment, viewed from the positive side of the Z-axis. FIG. 5B is aschematic side view of the light emitting device 100 according to thefirst embodiment, viewed from the positive side of the X-axis. FIG. 5Cis a schematic side view of the light emitting device 100 according tothe first embodiment, viewed from the positive side of the Y-axis.

The light emitting device 100 according to the first embodiment includesa plurality of light emitting elements 10 including a first lightemitting element 10A, a second light emitting element 10B, and a thirdlight emitting element 10C, and a case 20 that encloses the plurality oflight emitting elements 10.

In the example placement shown in FIG. 4B, each of the light emittingelements 10A, 10B, and 10C emits light in the negative direction of theY-axis. Three reflectors R are disposed in the interior of the case 20,each configured to reflect the light emitted from a corresponding one ofthe three light emitting elements 10 in the positive direction of theZ-axis. Also, as shown in FIG. 4A, the case 20 has a cover 32 includinga light-transmissive region that allows light reflected by the reflectorR passes therethrough. In this example, the entire cover 32 is formedfrom a light-transmissive material and serves as the light-transmissiveregion. Instead of the entire part of the cover 32, a portion of thecover 32 may serve as a light-transmissive region. The light emittingdevice 100 includes a plurality of main lenses 40: a first main lens40A, a second main lens 40B, and a third main lens 40C, covering atleast portions of the cover 32, and a plurality of sub-lenses 50disposed in the interior of the case 20: a first sub-lens 50A, a secondsub-lens 50B and a third sub-lens 50C. In this example, each of theplurality of sub-lenses 50 is disposed between a corresponding one ofthe plurality of light emitting elements 10 and a corresponding one ofthe plurality of reflectors R.

Next, with reference to FIG. 6 , FIG. 7 and FIG. 8 , the configurationof the light emitting device 100 according to the first embodiment willbe described in detail. FIG. 6 is a schematic cross-sectional view ofthe light emitting device 100 according to the first embodiment. FIG. 7is a schematic plan view showing the internal configuration of the lightemitting device 100, in which the cover 32 and the main lenses 40 arenot shown. FIG. 8 is a schematic perspective view showing aconfiguration example of a lens array 400 that can be used in the lightemitting device 100.

As shown in FIG. 6 , case 20 of light emitting device 100 has a base 22supporting light emitting element 10 and a cover 32 covering lightemitting element 10. The cover 32 can be formed from alight-transmissive material such as sapphire. The cover 32 includes, forexample, a plate formed from a light-transmissive material. A metallayer may be disposed on a surface of the plate. The base 22 includes abottom portion 24 having a first upward-facing surface on which aplurality of light emitting elements 10 are disposed, and a frameportion 26 surrounding the plurality of light emitting elements 10 andhaving a second upward-facing surface. The main lenses 40 are disposedon the cover 32 and the cover 32 is supported by the secondupward-facing surface of the frame portion 26.

The base 22 includes an electrode structure to electrically connect thelight emitting elements 10 to an external power source. The plurality oflight emitting elements 10 are electrically connected to the electrodestructure. Therefore, the base 22 also serves to electrically connectthe light emitting elements 10 to the external power supply. The base 22can be formed from a composite of an electrically insulating materialand an electrically conductive material. The base 22 includes, forexample, an electrically insulating ceramic body and an electricallyconductive metal part that serves as electrodes.

In the example shown in FIG. 6 , the frame portion 26 has a step portionhaving a third upward-facing surface 28 between the second upward-facingsurface supporting the cover 32 and the first upward-facing surface ofthe bottom portion 24. At least portions of the electrode structure forconnecting the light emitting elements 10 to the external power supplycan be disposed on the third upward-facing surface 28 of the stepportion. A portion of the electrode structure can be a via electrodethat penetrates the base 22. The electrode structure and the lightemitting elements 10 can be electrically connected, for example, viarespective wires. In FIG. 6 , the wires are not shown. In FIG. 7 , sixwires 60 are schematically illustrated. The wires 60 electricallyconnect the electrically conductive layers that are parts of theelectrode structure disposed on the third upward-facing surface 28 ofthe step portion and the light emitting elements 10 respectively. InFIG. 7 , the wires 60 are shown in the shape of straight lines, but thewires 60 may have, for example, curved portion(s) or bent portion(s).

In the example shown in FIG. 6 , each of the light emitting elements 10is secured to a corresponding one of the sub-mounts 12, and thesub-mounts 12 are secured to the base 22. The sub-mounts 12 can beomitted from the configuration of the light emitting device 100. Thesub-mounts 12 can be formed from a material having a thermalconductivity higher than the thermal conductivity of the base 22 toincrease heat dissipation. The light-emitting region of each of thelight emitting elements 10 is located opposite to the correspondingreflector R such that the light L is emitted toward the reflector R. InFIG. 6 , an optical axis (center) of light L is schematically depictedas a straight arrow. A plurality of sub-lenses 50 are disposed betweenthe light-emitting regions of the light emitting elements 10 and thereflectors R, respectively. The positions of the sub-lenses 50 areadjusted to compensate for positional deviations of corresponding one ofthe light emitting elements 10, and then the sub-lenses 50 are securedto the base 22. The expression “compensation” shown above does notnecessarily mean strict matching of the focal point of the lens systemformed by a combination of one of the main lenses 40 and a correspondingone of the sub-lenses 50 onto the light-emitting region of acorresponding one of the light emitting elements 10. “Compensation”includes adjusting the position and/or orientation of the sub-lens 50such that the focal point of the lens system is brought relatively closeto the light-emitting region of the light emitting element 10 comparedto that without the sub-lenses 50.

The position and orientation of each of the sub-lenses 50 are preferablyadjusted such that the focal point of the lens system formed by acombination of one of the main lenses 40 and a corresponding one of thesub-lenses 50 matches the light-emitting region of the light emittingelement 10. This allows each portion of light L that has passed throughthe corresponding one of the sub-lenses 50 to be more reliablycollimated or converged by the corresponding one of the main lenses 40.It is also preferable that at least one of the main lenses 40 and thesub-lenses 50 is not a lens array with a plurality of lensesmechanically connected together, but that the lenses are separate lenscomponents. This allows for a wider adjustment range for the focal pointof each combination of the main lens 40 and the sub-lens 50, compared toa case in which both the main lenses 40 and the sub-lenses 50 arerespectively provided as lens arrays. Accordingly, the focal point canbe easily matched to the light emitting region of a corresponding one ofthe light emitting elements 10.

Each of the reflectors R has a light-reflecting surface on at least oneside. The light-reflecting surface is inclined with respect to thebottom surface of the reflector R to reflect light L from the lightemitting element 10 toward the light-transmissive region. The reflectorR receives the radiation light from the light emitting element 10,therefore preferably be formed from a heat-resistant material. Thelight-reflecting surface can be formed with a layer of a material havinghigh reflectance. The main body part of the reflector R can be formedfrom glass such as quartz or BK7 (borosilicate glass), a metal such asaluminum, or Si. The light-reflecting surface can be formed from a metallayer and/or a dielectric multilayer film.

It is preferable that a portion of each of the sub-lenses 50 has a shapethat allows bonding to the base 22, for example, a rectangularparallelepiped shape. Each of the sub-lenses 50 has a curved-surfacelens portion. This curved surface can be convex or concave. Thesub-lenses 50 can be made of, for example, glass such as BK7 or B270.The main lenses 40 can also be made of, for example, glass such as BK7or B270. The main lens 40 contains three main lenses 40A, 40B and 40Carranged in an X axis direction as shown in FIG. 4A. Each of the mainlenses 40A, 40B, and 40C has a spherical or an aspherical lens shape ata portion where light L passes through, and has appropriate shapes atother portions. In the example shown in FIG. 4A, the lens shape portionof each of the main lenses 40 is a convex portion protruding upward froma plate-like portion. Close arrangement of the convex portions of theplurality of main lenses 40 can facilitate miniaturization of the lightemitting device 100. The distance between each of the convex portions ofthe plurality of main lenses 40 can be, for example, smaller than thewidth in the X-axis direction of a single convex portion.

The main lenses 40A, 40B, and 40C may be bonded to the cover 32 asseparate lens components, or may be secured to the cover 32 as a singleintegrated lens array. FIG. 8 is a schematic perspective view showing aconfiguration example of a lens array 400 in which the main lenses 40A,40B, and 40C are connected to each other. The lens array 400 is aone-piece body with the main lenses 40A, 40B, and 40C in a tightlyaligned structure along the X-axis. There may be a gap between the firstmain lens 40A and the second main lens 40B, and between the second mainlens 40B and the third main lens 40C, or the three main lenses 40A, 40B,and 40C may be connected without a gap.

As shown in FIG. 6 , the main lenses 40 can be secured to the cover 32via a bonding layer 34. The bonding layer 34 can be formed fromultraviolet curable resin, for example. The lens array 400 shown in FIG.8 can also be secured to the cover 32 via a similar bonding layer. Inthe lens array 400, the relative positional relationship among the mainlenses 40A, 40B, and 40C are in a fixed state, such that the main lenses40A, 40B, and 40C are not required to be secured separately to the cover32. The lens array 400 can be handled as a single component and thus canfacilitate mounting.

The plurality of light emitting elements 10 may emit light of differentcolors. For example, light emitting elements 10 respectively emittinglight of blue color, green color, and red color can be employed. In thefirst embodiment, the first light emitting element 10A, the second lightemitting element 10B, and the third light emitting element 10C can berespectively a green semiconductor laser element to emit a green laserbeam, a blue semiconductor laser element to emit a blue laser beam, anda red semiconductor laser element to emit a red laser beam. All of themare edge-emitting semiconductor laser elements.

The peak wavelength of the laser beam emitted by the blue semiconductorlaser element is in a range of 430 to 480 nm and may be in a range of450 to 470 nm. The peak wavelength of the laser beam emitted by thegreen semiconductor laser element is in a range of 500 to 550 nm and maybe in a range of 520 to 540 nm. The peak wavelength of the laser beamemitted by the red semiconductor laser element is in a range of 620 to660 nm and may be in a range of 630 to 650 nm. The blue semiconductorlaser element and the green semiconductor laser element can be formedmainly from nitride semiconductors. Examples of nitride semiconductorsinclude GaN, InGaN, and AlGaN. The red semiconductor laser element canbe formed mainly of a gallium arsenic-based semiconductor. When laserelements are employed as the light emitting elements 10, the higher theoptical energy is, the more accumulation of dust etc., from theenvironmental atmosphere attracted on the light-emitting surfaces of thelaser elements in operation. Dust and other particles on thelight-emitting surface can reduce the optical output. The optical energyincreases with shorter wavelengths of the laser beam, and with higheroptical output. For this reason, when laser elements to emit laser beamsof green color or shorter wavelengths are employed as the light emittingelements 10, the light emitting elements 10 are preferably hermeticallysealed within the case 20. When the light emitting elements 10 arehermetically sealed within the case 20, outside dust etc., can beprevented from entering the case 20, such that possibility of dust etc.,attaching to the light emitting surfaces of the laser elements can bereduced.

Lasing performance fluctuation due to temperature may more likely occurin red semiconductor laser elements than in blue and green semiconductorlaser elements. Blue semiconductor laser elements have a powerconversion efficiency greater than that of green semiconductor laserelements, and thus the amount of heat generated from the bluesemiconductor laser elements is smaller than that from the greensemiconductor laser elements. For this reason, the green semiconductorlaser elements are preferably disposed spaced apart from the redsemiconductor laser elements. As shown in FIG. 7 , in the firstembodiment, the blue semiconductor laser element (a second lightemitting element 10B) is disposed between the red semiconductor laserelement (a third light emitting element 10C) and the green semiconductorlaser element (a first light emitting element 10A). With thisconfiguration, the emission characteristics of the red semiconductorlaser element (the third light emitting element 10C) can be stabilized.

One or more semiconductor elements other than the light emittingelements 10 may be disposed in the case 20. For example, a protectivecircuit element such as a Zener diode configured to control reversevoltage loaded on respective light emitting elements 10 within apredetermined level and/or a photodetection element such as a photodiodeconfigured to monitor the intensity of light L may also be disposed.

In the first embodiment, each of the sub-lenses 50 can be disposed closeto the light-emitting region of a corresponding one of the lightemitting elements 10, such that light L emitted from each of thelight-emitting regions enters the sub-lens 50 before expanding. Thisallows for reducing the size of the sub-lenses 50. Further, adjustingthe positions of the sub-lenses 50 within the case 20 allows forcompensating for positional deviation of the light-emitting regions.Other than that shown in the figures, the shapes and dimensions of thesub-lenses 50 can be appropriately determined. In addition, when thebeam sizes of light L emitted from the plurality of light emittingelements 10 at the light incidence surfaces of the main lenses 40 differwithout the sub-lenses 50, it is possible to adjust the beam size ofeach portion of light L to approach uniformity by using the sub-lenses50.

Second Embodiment

A second embodiment of the present invention will be described belowwith reference to FIG. 9A through FIG. 12 .

A schematic configuration of a light emitting device 100 according tothe second embodiment will be described below with reference to FIG. 9A,FIG. 9B, FIG. 10A, FIG. 10B, and FIG. 10C. FIG. 9A is a schematicperspective view of a light emitting device according to the secondembodiment. FIG. 9B is a schematic perspective view showing an interiorof the light emitting device according to the second embodiment. FIG.10A is a schematic top view of the light emitting device shown in FIG.9A, viewed from the positive side of the Z-axis. FIG. 10B is a schematiclateral view of the light emitting device shown in FIG. 9A, viewed fromthe positive side of the X-axis. FIG. 10C is a schematic lateral view ofthe light emitting device shown in FIG. 9A, viewed from the positiveside of the Y-axis.

As in the light emitting device 100 according to the first embodimentdescribed above, the light emitting device 100 according to the secondembodiment includes a plurality of light emitting elements 10 thatincludes a first light emitting element 10A, a second light emittingelement 10B, and a third light emitting element 10C, a case 20 enclosingthe plurality of light emitting elements 10. The difference from thefirst embodiment is the configuration of a plurality of sub-lenses 50disposed in the case 20. The difference will be described in detailbelow.

As shown in FIG. 9B, the light emitting device 100 according to thesecond embodiment includes a first sub-lens 50A, a sub-lens 50B, and athird sub-lens 50C. In the second embodiment, the plurality ofsub-lenses 50 are respectively disposed between the cover 32 and acorresponding one of the reflectors R.

Next, with reference to FIG. 11 and FIG. 12 , structure of thesub-lenses 50 of the light emitting device 100 according to the secondembodiment will be described. FIG. 11 is a schematic cross-sectionalview showing the light emitting device 100 according to the secondembodiment. FIG. 12 is a schematic plan view showing a structure of aninterior of the light emitting device 100. In FIG. 12 , the cover 32 andthe main lenses 40 are not shown.

As shown in FIG. 11 , the case 20 of the light emitting device 100 inthe second embodiment also includes a base 22 configured to support theplurality of light emitting elements 10, and a cover 32 configured tocover the plurality of light emitting elements 10. The base 22 includesa bottom portion 24 having a first upward-facing surface on which aplurality of light emitting elements 10 and a plurality of reflectors Rare disposed, and a frame portion 26 surrounding the plurality of lightemitting elements 10 and having a second upward-facing surface. Thelight emitting elements 10 are surrounded by the frame portion 26. Themain lenses 40 are disposed on the cover 32 and the cover 32 issupported by the second upward-facing surface of the frame portion 26.The main lenses 40 may be provided as the lens array 400 shown in FIG. 8.

In the example shown in FIG. 11 , the frame portion 26 has two stepportions (an upper step portion and a lower step portion) respectivelyhaving an upward-facing surface between the second upward-facing surfacesupporting the cover 32 and the first upward-facing surface of thebottom portion 24. At least a portion of the electrode structure toconnect the light emitting elements 10 to an external power source canbe disposed on the upward-facing surface 28A of the lower step portion.In the second embodiment, each of the plurality of sub-lenses 50 issupported by the upward-facing surface 28B of the upper step portion ofthe frame portion 26.

In FIG. 11 and FIG. 12 , the wires are not shown. The light emittingdevice 100 according to the second embodiment also includes theelectrode structure and wires as described in the first embodiment, andthe repetitive description of which will be omitted.

As shown in FIG. 12 , each of the sub-lenses 50A, 50B, and 50C has aplate-like flat extending portion 52 and a lens shape having convexportion with a curved surface. The convex portion serves as a lens. Thesub-lenses 50A, 50B, and 50C are respectively discrete components and,for example, made of a glass material. Each of the sub-lenses 50A, 50B,and 50C has a substantially rectangular shape in a plan view, with alength L1 in a Y-axis direction that allows each of the sub-lens 50A,50B, and 50C to rest on the left portion and the right portion of theupward-facing surface 28B of the frame portion 26. Both ends of each ofthe sub-lenses 50A, 50B, and 50C are slidably supported by theupward-facing surface 28B of the frame portion 26 and can be slid in anX-axis direction before being secured to the frame portion 26. Beforebeing secured to the frame portion 26, each of the sub-lenses 50A, 50B,and 50C can also be slid in a Y-axis direction. In order to allow suchsliding in the Y-axis direction, the length L1 in a Y-axis direction oflateral surfaces extending from outer edges of the upward-facing surface28B in a positive Z-axis direction is greater than the length L2 of eachof the sub-lenses 50A, 50B, and 50C. The length L1 may also be referredto a distance between the left end of the left side portion of theupward-facing surface 28B and the right end of the right side portion ofthe upward-facing surface 28B in the Y-axis direction. A difference inthe lengths (L1-L2) determines an upper limit of shiftable range of thesub-lenses 50A, 50B, and 50C in the Y-axis direction. The difference inthe lengths (L1-L2) can be set within a range appropriate for thedimensions of the light emitting device 100. The length L2 may be set,for example, in a range of 0.5 to 0.95 times with respect to the lengthL1. The difference in the lengths (L1-L2) can be set, for example,within a range of 0.2 to 3 mm. In order to allow the upward-facingsurface 28B to support the both ends of the sub-lenses 50A, 50B, and50C, the length L3 in the Y-axis direction of lateral surfaces extendingfrom inner edges of the upward-facing surface 28B in a negative Z-axisdirection is less than the length L2 of each of the sub-lenses 50A, 50B,and 50C. The length L3 may also be referred to a distance between theright end of the left side portion of the upward-facing surface 28B andthe left end of the right side portion of the upward-facing surface 28Bin the Y-axis direction. The length L3 may be set, for example, in arange of 0.5 to 0.95 times with respect to the length L2. The differencein the lengths (L2-L3) can be set, for example, within a range of 0.02to 3 mm.

In the second embodiment, at the time of securing the sub-lenses 50A,50B, and 50C to the frame portion 26, each of the sub-lenses is allowedto be slided in the two dimensions along the upward-facing surface 28Bof the step portion, which facilitates the positional adjustment of thesub-lenses 50A, 50B, and 50C.

The positions of the sub-lenses 50A, 50B, and 50C in the Z-axisdirection can be adjusted by a thickness of a bonding layer disposedbetween the upward-facing surface 28B of the step portion and the lowersurfaces of the sub-lenses 50A, 50B, and 50C.

As described in the first embodiment, when the sub-lenses 50A, 50B, 50Care secured to the case 20 by using a ultraviolet curable resin,adjustment can be performed with uncured ultraviolet curable resin beingdisposed between the sub-lenses 50A, 50B, and 50C and the upward-facingsurface 28B of the step portion. After the positions and theorientations of the sub-lenses 50A, 50B, and 50C are adjusted, thepositions and the orientations of the sub-lenses 50A, 50B, and 50C areheld by a jig or a holding device, and ultraviolet light is irradiatedto harden the resin.

In the light emitting device 100 according to the second embodiment, theplurality of sub-lenses 50 are respectively held by the step portion ofthe frame portion 26. This arrangement allows for arranging thesub-lenses 50 at higher locations than the light emitting elements 10and the reflectors R, which can facilitate handling of the sub-lenses50A, 50B, and 50C, and which can facilitate positioning of thesub-lenses 50A, 50B, and 50C in X-Y plane. Meanwhile, the shiftablerange of the sub-lenses 50A, 50B, and 50C along the propagationdirection of light, that is, along the optical axis can be greater inthe first embodiment than in the second embodiment. Also, the firstembodiment is more advantageous in view of miniaturizing of the lightemitting device. This is because in the second embodiment, distancesbetween the light-emitting regions of the light emitting elements 10 anda corresponding one of the sub-lenses 50 becomes relatively great,resulting in relatively large convex portions that serve as lenses inthe sub-lenses 50.

In the embodiments described above, the light emitting devices 100 areprovided with the reflectors R, but the reflectors R can be optional.

Third Embodiment

A third embodiment of the present invention will be described below withreference to FIG. 13A to FIG. 16 . A light emitting device 100 accordingto the third embodiment is not provided with a reflector R.

A general structure of a light emitting device 100 according to thethird embodiment will be described below with reference to FIG. 13A,FIG. 13B, FIG. 14A, FIG. 14B, and FIG. 14C. FIG. 13A is a schematicperspective view showing a light emitting device according to the thirdembodiment. FIG. 13B is a schematic perspective view showing an interiorof the light emitting device according to the third embodiment. FIG. 14Ais a schematic top view of and the emitting device according to thethird embodiment, viewed from the positive Z-axis. FIG. 14B is aschematic lateral view of the light emitting device according to thethird embodiment, viewed from the positive X-axis. FIG. 14C is aschematic lateral view of the light emitting device according to thethird embodiment, viewed from the positive Y-axis.

As in the first embodiment and the second embodiment described above,the light emitting device 100 according to the third embodiment includesa plurality of light emitting elements 10, which include a first lightemitting element 10A, a second light emitting element 10B, and a thirdlight emitting element 10C, as well as a case 20 enclosing the pluralityof light emitting elements 10. The light emitting device 100 accordingto the third embodiment is not provided with a reflector R. Lightemitted from each of the plurality of light emitting elements 10disposed in the case 20 is extracted from a lateral surface of the case20. This will be described in detail below. The case 20 has a lid 70covering a frame portion 26. In FIG. 13B, the lid 70 and main lenses 40are not shown.

As shown in FIG. 13A, the light emitting device 100 according to thethird embodiment includes a first main lens 40A, a second main lens 40B,and a third main lens 40C, respectively secured on a cover 32 located ona lateral surface of the case 20. The light emitting device 100according to the third embodiment includes a first sub-lens 50A, asub-lens 50B, and a third sub-lens 50C located in the case 20. In thethird embodiment, the first sub-lens 50A is located in the optical pathbetween the first light emitting element 10A and the first main lens40A. The second sub-lens 50B is located in the optical path between thesecond light emitting element 10B and the second main lens 40B. Thethird sub-lens 50C is located in the optical path between the thirdlight emitting element 10C and the third main lens 40C.

Next, with reference to FIG. 15 and FIG. 16 , the structure of the lightemitting device 100 according to the third embodiment will be furtherdescribed. FIG. 15 is a schematic cross-sectional view showing the lightemitting device 100 according to the third embodiment. FIG. 16 is aschematic plan view showing a structure of an interior of the lightemitting device 100, in which a lid 70 is not shown.

As shown in FIG. 15 , in the third embodiment, a through opening 26X isformed in a lateral surface, more specifically, a portion of the frameportion 26 of the case 20. The through opening 26X of the frame portion26 is covered by a cover 32. The main lenses 40 are secured to the frameportion 26 via a bonding layer 34. Alternatively, the main lenses 40 maybe secured to the cover 32.

Light L is emitted from each of the light emitting elements 10A, 10B,and 10C in the positive Y-axis. Three sub-lenses 50 are disposed in theinterior of the case 20 to transmit light emitted from a correspondingone of the three light emitting elements 10.

The lid 70 is not required to have a light-transmissive portion, but thecover 32 is required to have a light-transmissive portion. At least aportion of the cover 32 to transmit light L is made of alight-transmissive material. Light L that has passed through each one ofthe sub-lenses 50 can be collimated or converged by a corresponding oneof the main lenses 40. Adjustment and securing of each of the sub-lenses50 can be performed as described in the first embodiment. The lightemitting device 100 according to the third embodiment also includes theelectrode structure and wires as described above.

According to the structure in the third embodiment, a reflector R is notrequired in the light emitting device 100, which allows a reduction inthe number of components, which in turn allows a reduction in thedimensions of the light emitting device 100.

The embodiments described above are intended as illustrative of a lightemitting device to give a concrete form to technical ideas of thepresent invention, and the scope of the invention is not limited tothose described below. Further, the members shown in claims attachedhereto are not specifically limited to members according to embodiments.The sizes, materials, shapes and the relative configuration etc. ofcomponents described in the embodiments are given as an example and notas a limitation to the scope of the invention, unless specificallydescribed otherwise.

In addition, in the present disclosure, a plurality of structuralelements may be configured as a single part that serves the purpose of aplurality of elements, and on the other hand, a single structuralelement may be configured as a plurality of parts that serve the purposeof a single element.

The light emitting devices according to the present disclosure can beused as light sources of projectors, vehicular headlights, lightingdevices, communication devices, laser machining devices, etc.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

What is claimed is:
 1. A light emitting device comprising: a pluralityof laser elements including a first laser element and a second laserelement; a case enclosing the plurality of laser elements, the casecomprising a base, the base comprising: a bottom portion having anupward-facing surface that supports the plurality of laser elements, anda frame portion surrounding the plurality of laser elementes and havinga lateral surface that intersects with the upward-facing surface,wherein an opening extends through the frame portion, the openingconfigured to allow light emitted from the plurality of laser elementsto transmit through the opening; and a plurality of main lenses secureddirectly or indirectly over the opening of the case including a firstmain lens configured to collimate or converge light emitted from thefirst laser element and a second main lens configured to collimate orconverge light emitted from the second laser element; wherein: at leasta first portion of the opening is disposed on a first imaginary linepassing through a light emitting end surface of the first laser elementand the first main lens, and at least a second portion of the opening isdisposed on a second imaginary line passing through a light emitting endsurface of the second laser element and the second main lens.
 2. Thelight emitting device according to claim 1, further comprising: aplurality of sub-lenses disposed in the case, the plurality ofsub-lenses including a first sub-lens located in an optical path betweenthe first light emitting element and the first main lens, and a secondsub-lens located in an optical path between the second light emittingelement and the second main lens.
 3. The light emitting device accordingto claim 2, wherein: the plurality of sub-lenses is spaced apart fromthe plurality of laser elements and the opening of the frame portion. 4.The light emitting device according to claim 2, wherein: the pluralityof main lenses is disposed outside the case.
 5. The light emittingdevice according to claim 2, wherein: a position and an orientation ofthe first sub-lens are such that a focal point of a combination of thefirst main lens and the first sub-lens is on a plane of a light-emittingregion of the first laser element; and a position and an orientation ofthe second sub-lens are such that a focal point of a combination of thesecond main lens and the second sub-lens is on a plane of alight-emitting region of the second laser element.
 6. The light emittingdevice according to claim 2, wherein: each of the plurality ofsub-lenses compensates for an alignment deviation between acorresponding one of the plurality of main lenses and a correspondingone of the plurality of laser elements.
 7. The light emitting deviceaccording to claim 2, wherein: the plurality of laser elements include athird laser element; the plurality of main lenses include a third mainlens configured to collimate or converge light emitted from the thirdlaser element; and the plurality of sub-lenses include a third sub-lenslocated in an optical path between the third laser element and the thirdmain lens.
 8. The light emitting device according to claim 7, wherein:the first laser element is configured to emit blue light, the secondlaser element is configured to emit green light, and the third laserelement is configured to emit red light.
 9. The light emitting deviceaccording to claim 1, wherein: the case comprises a cover attached tothe frame portion so as to cover the opening, wherein the covercomprises a light-transmissive portion.
 10. The light emitting deviceaccording to claim 1, wherein: the plurality of main lenses are includedin a lens array in which the first main lens and the second main lensare connected.
 11. The light emitting device according to claim 1,wherein: the first laser element is configured to emit light having afirst peak wavelength; and the second laser element is configured toemit light having a second peak wavelength that is different from thefirst peak wavelength.